Most IRFs are dependent on parameters, and the 1-dimensional parameter arrays are stored in columns. The following names are recommended:
- For energy grids, see here
for basic recommendations. Column names should be
ENERG_HIbecause that is used (consistently I think) for OGIP and Fermi-LAT. For separate HDUs, the extension names should be
EBOUNDS(used by Fermi-LAT consistently).
- Sky coordinates should be called
- Field of view coordinates
PHIfor offset and position angle in the field of view (see Field of view).
- Offset wrt. the source position should be called
RAD(this is what the OGIP PSF formats use).
In the specific case of point-like IRFs:
- The energy-dependent radius of the selected region of interest should be
The IRF format specifications mention a recommended axis format and axis units. But tools should not depend on this and instead:
- Use the axis order specified by the
CREFheader keyword (see BINTABLE HDU)
- Use the axis unit specified by the
CUNITheader keywords (see BINTABLE HDU)